Thank you. I would use an angle grinder and first cut some strait lines to the edge of the circle, then around the circles perimeter, and finish with a cement finishing tool.
I see what you're saying but it will sit on a metal crossbar and I thought the epoxy would give it additional strength. Otoh, it might be less hassle and more peace of mind just going with plywood.
Just a really bad idea!
It would be cheaper and faster to just by a new table.
The only time I've seen this work out is when the guy cut out a piece of 4 X 8 X 3/4" PVC to fit.
It worked perfect, but looked like poop.